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Subject: Re: [PATCH 0/3] Collapse vimc into single monolithic driver
To:     =?UTF-8?Q?Andr=c3=a9_Almeida?= <andrealmeid@collabora.com>,
        mchehab@kernel.org, helen.koike@collabora.com, hverkuil@xs4all.nl,
        laurent.pinchart@ideasonboard.com
Cc:     linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        kernel@collabora.com,
        "skh >> Shuah Khan" <skhan@linuxfoundation.org>
References: <cover.1565386363.git.skhan@linuxfoundation.org>
 <3118bc46-14ac-8015-9a6c-a8dfcdcea940@collabora.com>
 <4e9b8eb3-23c5-62ea-07dc-b51acb238dee@linuxfoundation.org>
 <15badf5e-49fa-7fbe-de6b-296e9a7f5cd9@collabora.com>
From:   Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <daca7cbc-7ace-71e1-c797-c4db9c4f79a8@linuxfoundation.org>
Date:   Fri, 9 Aug 2019 18:48:32 -0600
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On 8/9/19 6:24 PM, André Almeida wrote:
> On 8/9/19 9:17 PM, Shuah Khan wrote:
>> Hi Andre,
>>
>> On 8/9/19 5:52 PM, André Almeida wrote:
>>> Hello Shuah,
>>>
>>> Thanks for the patch, I did some comments below.
>>>
>>> On 8/9/19 6:45 PM, Shuah Khan wrote:
>>>> vimc uses Component API to split the driver into functional components.
>>>> The real hardware resembles a monolith structure than component and
>>>> component structure added a level of complexity making it hard to
>>>> maintain without adding any real benefit.
>>>>       The sensor is one vimc component that would makes sense to be a
>>>> separate
>>>> module to closely align with the real hardware. It would be easier to
>>>> collapse vimc into single monolithic driver first and then split the
>>>> sensor off as a separate module.
>>>>
>>>> This patch series emoves the component API and makes minimal changes to
>>>> the code base preserving the functional division of the code structure.
>>>> Preserving the functional structure allows us to split the sensor off
>>>> as a separate module in the future.
>>>>
>>>> Major design elements in this change are:
>>>>       - Use existing struct vimc_ent_config and struct
>>>> vimc_pipeline_config
>>>>         to drive the initialization of the functional components.
>>>>       - Make vimc_ent_config global by moving it to vimc.h
>>>>       - Add two new hooks add and rm to initialize and register,
>>>> unregister
>>>>         and free subdevs.
>>>>       - All component API is now gone and bind and unbind hooks are
>>>> modified
>>>>         to do "add" and "rm" with minimal changes to just add and rm
>>>> subdevs.
>>>>       - vimc-core's bind and unbind are now register and unregister.
>>>>       - vimc-core invokes "add" hooks from its vimc_register_devices().
>>>>         The "add" hooks remain the same and register subdevs. They don't
>>>>         create platform devices of their own and use vimc's pdev.dev as
>>>>         their reference device. The "add" hooks save their
>>>> vimc_ent_device(s)
>>>>         in the corresponding vimc_ent_config.
>>>>       - vimc-core invokes "rm" hooks from its unregister to unregister
>>>> subdevs
>>>>         and cleanup.
>>>>       - vimc-core invokes "add" and "rm" hooks with pointer to struct
>>>> vimc_device
>>>>         and the corresponding struct vimc_ent_config pointer.
>>>>       The following configure and stream test works on all devices.
>>>>            media-ctl -d platform:vimc -V '"Sensor
>>>> A":0[fmt:SBGGR8_1X8/640x480]'
>>>>       media-ctl -d platform:vimc -V '"Debayer
>>>> A":0[fmt:SBGGR8_1X8/640x480]'
>>>>       media-ctl -d platform:vimc -V '"Sensor
>>>> B":0[fmt:SBGGR8_1X8/640x480]'
>>>>       media-ctl -d platform:vimc -V '"Debayer
>>>> B":0[fmt:SBGGR8_1X8/640x480]'
>>>>            v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v
>>>> width=1920,height=1440
>>>>       v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81
>>>>       v4l2-ctl -z platform:vimc -d "Raw Capture 1" -v pixelformat=BA81
>>>>            v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video1
>>>>       v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video2
>>>>       v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video3
>>>>
>>>> The third patch in the series fixes a general protection fault found
>>>> when rmmod is done while stream is active.
>>>
>>> I applied your patch on top of media_tree/master and I did some testing.
>>> Not sure if I did something wrong, but just adding and removing the
>>> module generated a kernel panic:
>>
>> Thanks for testing.
>>
>> Odd. I tested modprobe and rmmod both.I was working on Linux 5.3-rc2.
>> I will apply these to media latest and work from there. I have to
>> rebase these on top of the reverts from Lucas and Helen
> 
> Ok, please let me know if I succeeded to reproduce.
> 
>>>
>>> ~# modprobe vimc
>>> ~# rmmod vimc
>>> [   16.452974] stack segment: 0000 [#1] SMP PTI
>>> [   16.453688] CPU: 0 PID: 2038 Comm: rmmod Not tainted 5.3.0-rc2+ #36
>>> [   16.454678] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>>> BIOS 1.12.0-20181126_142135-anatol 04/01/2014
>>> [   16.456191] RIP: 0010:kfree+0x4d/0x240
>>>
>>> <registers values...>
>>>
>>> [   16.469188] Call Trace:
>>> [   16.469666]  vimc_remove+0x35/0x90 [vimc]
>>> [   16.470436]  platform_drv_remove+0x1f/0x40
>>> [   16.471233]  device_release_driver_internal+0xd3/0x1b0
>>> [   16.472184]  driver_detach+0x37/0x6b
>>> [   16.472882]  bus_remove_driver+0x50/0xc1
>>> [   16.473569]  vimc_exit+0xc/0xca0 [vimc]
>>> [   16.474231]  __x64_sys_delete_module+0x18d/0x240
>>> [   16.475036]  do_syscall_64+0x43/0x110
>>> [   16.475656]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>> [   16.476504] RIP: 0033:0x7fceb8dafa4b
>>>
>>> <registers values...>
>>>
>>> [   16.484853] Modules linked in: vimc(-) videobuf2_vmalloc
>>> videobuf2_memops v4l2_tpg videobuf2_v4l2 videobuf2_common
>>> [   16.486187] ---[ end trace 91e5e0894e254d49 ]---
>>> [   16.486758] RIP: 0010:kfree+0x4d/0x240
>>>
>>> <registers values...>
>>>
>>> fish: “rmmod vimc” terminated by signal SIGSEGV (Address boundary error)
>>>
>>> I just added the module after booting, no other action was made. Here is
>>> how my `git log --oneline` looks like:
>>>
>>> 897d708e922b media: vimc: Fix gpf in rmmod path when stream is active
>>> 2e4a5ad8ad6d media: vimc: Collapse component structure into a single
>>> monolithic driver
>>> 7c8da1687e92 media: vimc: move private defines to a common header
>>> 97299a303532 media: Remove dev_err() usage after platform_get_irq()
>>> 25a3d6bac6b9 media: adv7511/cobalt: rename driver name to adv7511-v4l2
>>> ...
>>>
>>>>
>>>> vimc_print_dot (--print-dot) topology after this change:
>>>> digraph board {
>>>>      rankdir=TB
>>>>      n00000001 [label="{{} | Sensor A\n/dev/v4l-subdev0 | {<port0>
>>>> 0}}", shape=Mrecord, style=filled, fillcolor=green]
>>>>      n00000001:port0 -> n00000005:port0 [style=bold]
>>>>      n00000001:port0 -> n0000000b [style=bold]
>>>>      n00000003 [label="{{} | Sensor B\n/dev/v4l-subdev1 | {<port0>
>>>> 0}}", shape=Mrecord, style=filled, fillcolor=green]
>>>>      n00000003:port0 -> n00000008:port0 [style=bold]
>>>>      n00000003:port0 -> n0000000f [style=bold]
>>>>      n00000005 [label="{{<port0> 0} | Debayer A\n/dev/v4l-subdev2 |
>>>> {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>>>>      n00000005:port1 -> n00000015:port0
>>>>      n00000008 [label="{{<port0> 0} | Debayer B\n/dev/v4l-subdev3 |
>>>> {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>>>>      n00000008:port1 -> n00000015:port0 [style=dashed]
>>>>      n0000000b [label="Raw Capture 0\n/dev/video1", shape=box,
>>>> style=filled, fillcolor=yellow]
>>>>      n0000000f [label="Raw Capture 1\n/dev/video2", shape=box,
>>>> style=filled, fillcolor=yellow]
>>>>      n00000013 [label="{{} | RGB/YUV Input\n/dev/v4l-subdev4 |
>>>> {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
>>>>      n00000013:port0 -> n00000015:port0 [style=dashed]
>>>>      n00000015 [label="{{<port0> 0} | Scaler\n/dev/v4l-subdev5 |
>>>> {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>>>>      n00000015:port1 -> n00000018 [style=bold]
>>>>      n00000018 [label="RGB/YUV Capture\n/dev/video3", shape=box,
>>>> style=filled, fillcolor=yellow]
>>>> }
>>>
>>> Since the topology changed, it would be nice to change in the
>>> documentation as well. The current dot file can be found at
>>> `Documentation/media/v4l-drivers/vimc.dot` and it's rendered at this
>>> page: https://www.kernel.org/doc/html/latest/media/v4l-drivers/vimc.html
>>>
>>
>> Topology shouldn't have changed. No changes to links or pads etc.
>> I will take a look to be sure. I agree that if topology changes
>> document should be updated.
> 
> If you "diff" the current dot with the dot you generated, you will see
> some differences. The main difference is that "RGB/YUV Input" was a
> device "/dev/video2/", and now it a subdevice "/dev/v4l-subdev4".
> 

Yeah. I should have saved dot before my changes and compare. The goal is
to not change anything. I will make sure topology doesn't change.

Thanks again for testing these patches quickly.

thanks,
-- Shuah